Effects of the High Power Ultrasound on Microorganisms in Fruit Juices

Submit Manuscript | http://medcraveonline.com 100 kHz) can provide the mechanical effect of cavitation in liquid systems which can alter physical and chemical properties of food depending on the type of material involved. When ultrasound waves pass through a medium, a series of compression and rarefaction waves on the molecules of the medium are produced. This enforces a sinusoidal acoustic pressure (Pa) in addition to the hydrostatic pressure acting on the medium. If a large negative pressure (sufficiently below ambient) is applied to the liquid so that the distance between the molecules exceeds the critical molecular distance necessary to hold the liquid intact, the liquid will break down and the cavitation bubbles will be formed. These bubbles are formed from the gas nuclei within the fluid and are distributed throughout the liquid. After a period of a few cycles, the bubbles will grow into a critical size which makes them unstable and collapse violently. Power ultrasound is technique that is used in processing of fruit and vegetable juices. Several mechanisms of inactivation of microorganisms have been proposed. The mechanical stress of ultrasound on cells suspended in liquid medium (hydrodynamic events: acoustic cavitation and cavitation induced microstreaming) and radical formation are proposed mechanisms for microbial inactivation. Physical and chemical factors affect fruits, vegetables and plant tissues by causing the excessive accumulation of reactive oxygen species (ROS). Reactive oxygen species can cause damage to membranes and other essential macromolecules such as proteins, DNA, and lipids [1].